Editor Shortcuts

I have modified the editor shortcuts: now "Cursor Down" is assigned to "CTRL-K" which for me is more practical. However, I've noticed that the behavior of the shortcut is different compared to when I press the down arrow. With the arrow if the cursor is, for example, on column 9 of the text, it will stay on column 9 of the text as long as there is enough text in the line. However, with the shortcut, if the cursor moves, let's say to column 2, because on a line there is not enough text, it will since then keep going down on column 2. Am I missing something? Many thanks in advance, Cesare